Far Side of the Moon

On October 3, 1957, the Soviet (Russian) space probe Luna 3 flew around the
far side of the moon and returned the first photographs ever seen of its hidden
side. The biggest surprise was that the far side was very plain compared to the
near side. The near side is covered with large dark lava plains, but the far
side has almost none. The lave plains were first thought to be seas and are
still given the Latin name mare (plural, maria) which means "sea."
The maria are now known to be huge craters later flooded by lava. Only two large
lava-filled craters were seen on the far side: a large one given the name Mare
Muscoviense (Latin for Moscow Sea) and a smaller one named Tsiolkovsky after the
Russian rocket pioneer Konstantin Tsiolkovsky. Almost no other craters are
visible because the far side of the moon was fully sunlit and there were no
shadows to reveal topography.

It is still not clear why one side of the moon was pummeled harder by the
huge meteorites that created the maria basins. Since the maria are filled by
dense lava flows, the earth's gravity caused that side of the Moon to face the
earth as the Moon stopped rotating.

The view here shows Luna 3 passing the far side of the Moon. Features on the
leftmost quarter of the Moon are visible from Earth; everything else is
completely hidden from terrestrial viewers. The spacecraft took photographs on film, developed the film
and scanned it on board, then sent the images back to earth. Digital imaging in
1959 was very crude compared to today, and the images are of poor quality
compared to what we can achieve now. The original scene shows one of the photos
as originally transmitted, and a composite of all the Luna 3 pictures processed
using modern computer technology.